Growth factor dependence of pheochromocytoma cells in chemically defined medium

We have previously described the isolation of a clonal pheochromocytoma cell line (PC-G2) which responds to nerve growth factor (NGF) [Goodman and Herschman, 1978] and epidermal growth factor (EGF) [Goodman et al, 1980] with increased specific activity of tyrosine hydroxylase (TH). This cell line thus can be used for studies of induction of a key enzyme in the biosynthesis of catecholamines using a homogeneous cell population under controlled environmental influences. However, the need for serum in the culture medium used to grow these cells still introduced a lack of total environmental control. Several laboratories have circumvented this problem by growing cells in chemically defined medium. In the present report we demonstrate that with a modification PC-G2 cells can survive and grow in the chemically defined N3 medium devised by Bottenstein and Sato [1979]. While another pheochromocytoma cell line, PC-12, was shown to grow in N3 medium without any supplement [Bottenstein et al, 1979], the PC-G2 cells exhibit an absolute requirement for NGF or EGF in order to grow in this chemically defined medium. As was the case in the induction of TH in serum-containing medium [Goodman and Herschman, 1978; Goodman et al. 1980], EGF was found to be 100 times more potent than NGF in the support of growth of the PC-G2 cells. In the present report we demonstrate not only that either of these growth factors will support the growth of the PC-G2 cells, but also that the relative potency of these two factors for support of the cell growth is similar to their relative potencies in the induction of tyrosine hydroxylase in serum-containing medium.